This invention relates to a cavity structure of an electric junction box in which an automotive fuse is mounted.
FIG. 4 shows a related-art electric junction box in which an automotive fuse is mounted.
In the cavity 40 shown in FIG. 4, a pair of tab (male) terminals 43 and 44, projecting from a bottom plate 42, are disposed within a housing receiving portion 41 having four side walls, and an upper end portion of the housing receiving portion 41 serves as a cavity opening 45. The pair of tab terminals 43 and 44 are connected serially to a circuit of an automotive electrical equipment.
Examples of automotive fuses to be mounted in such a cavity 40 are shown in FIGS. 5 and 6.
An automotive fuse 50, shown in FIG. 5, is a long-body plug-in fuse, and a cover 52 is provided at an upper end of a housing body 51 of a square tubular shape, and an opening 53 is formed at a lower end of the housing body 51. A pair of tab-receiving (female) terminals 54 and 55 are provided within the housing body 51, and are disposed relatively remote from the opening 53, and a fusible element 56 is integrally connected to upper ends of the tab-receiving terminals 54 and 55. The cover 52 is locked to the housing body 51 by a pair of locking pieces (not shown).
An automotive fuse 60, shown in FIG. 6, is a short-body plug-in fuse, and a cover 62 is provided at an upper end of a housing body 61 of a square tubular shape, and an opening 63 is formed at a lower end of the housing body 61. A pair of tab-receiving (female) terminals 64 and 65 are provided within the housing body 61, and are disposed relatively close to the opening 63, and a fusible element 66 is integrally connected to upper ends of the tab-receiving terminals 64 and 65.
A pair of elastic locking pieces 62a are formed respectively at opposite ends of the cover 62, and these locking pieces 62a can be locked respectively to a pair of retaining projections 61a formed respectively at corresponding portions of the housing body 61.
The opening 53, 63 of the automotive fuse 50, 60 is located in registry with the cavity opening 45, and the housing body 51, 61 is inserted into the housing receiving portion 41 until the opening 53, 63 is brought into contact with the bottom plate 42, so that the tab-receiving terminals 54 and 55 (64 and 65) are electrically connected to the tab terminals 43 and 44, respectively.
When a large current flows in the circuit, for example, as a result of development of seizure in the electrical equipment such as a motor, the fusible element 56, 66 melts to break the circuit so as to prevent an excess large current from flowing in the circuit, thus protecting the circuit.
The automotive fuses 50 and 60 are disclosed, for example, in Japanese Patent Publication No. 2001-325875A.
Usually, fuse cavities, together with switching devices (such as relays) are provided at a junction box or a specially-designed fuse box, and therefore it is not desired to form the fuse cavities into various shapes, and the fuse cavities are molded into a standardized single shape. Therefore, it has been desired that the cavity 40 should have the housing receiving portion 41 of a common construction for use with both of the long-body automotive fuse 50 and the short-body automotive fuse 60.
When the long-body automotive fuse 50 is mounted in the cavity 40, the housing body 51 is received within the housing receiving portion 41, with the distal ends of the tab terminals 43 and 44 considerably spaced from the fusible element 56 (see FIG. 5).
However, when the short-body automotive fuse 40 is mounted in the cavity, the housing body 61 is received within the housing receiving portion 41, with the distal ends of the tab terminals 43 and 44 disposed close to the fusible element 66, and therefore the tab terminals 43 and 44 are liable to interfere with the fusible element 66. When the tab terminals 43 and 44 interfered with the fusible element 66, there is anxiety that the housing body 61 could not be surely inserted into the housing receiving portion 41.
When the tab terminals 43 and 44 are designed such that the length of projecting of the tab terminals 43 and 44 within the housing receiving portion 41 is reduced, the above anxiety with the short-body automotive fuse 60 is overcome. However, since the length of projecting of the tab terminals 43 and 44 are short, the area of contact between each of the tab terminals 43 and 44 and the corresponding tab-receiving terminal 64, 65 of the long-body automotive fuse 60 is reduced, the electrical connection between the two would be unstable.
It is therefore an object of the invention is to provide a cavity structure of an electric junction box which has an enhanced general-purpose ability for use with various fuses.
In order to achieve the above object, according to the invention, there is provided an electric junction box, comprising:
a first housing, formed with a cavity adapted to receive both of a second housing having a first length and provided with a first fuse, and a third housing having a second length smaller than the first length and provided with a second fuse, the cavity having a bottom;
a pair of terminals, extending from the bottom of cavity so as to have a third length, and adapted to be fitted with both of the first fuse and the second fuse; and
at least one spacer, having a predetermined thickness smaller than the third length and removably disposed on the bottom of cavity, at least in a case where the third housing is received in the cavity.
Here, it is preferable that the predetermined thickness is determined so as to adjust a fitting amount of the third housing into the cavity.
It is also preferable that the predetermined thickness is determined so as to adjust a length of the terminals projected from a top face of the spacer.
It is also preferable that the predetermined thickness is determined so as to adjust a depth of the cavity.
In the above configuration, in a case where the terminals interfere with the fuse provided in the mating housing, the spacer is disposed so as to reduce the fitting amount of the mating housing into the cavity (the projected amount of the terminal from the top face of the spacer, or the depth of the cavity). On the other hand, in a case where the terminals do not interfere with the fuse, the spacer is not disposed.
Therefore, the different housings can be surely mounted in the first housing of the same construction, and there can be obtained the electric junction box having an enhanced general-purpose ability for use with the various fuses.
Preferably, an outline of the spacer is substantially identical with an outline of the bottom of the cavity.
It is also preferable that the spacer is formed with a pair of through holes through which the terminals are inserted.
In such configuration, since the terminals are prevented from being bent, the fuse is prevented from being displaced out of position.
Preferably, a color of the spacer is different from a color of the first housing.
In such a configuration, those cavities, each having the spacer mounted therein, can be easily distinguished from those cavities each having no spacer, and the erroneous mounting of the fuse can be surely prevented.